AES San Francisco 2008Poster Session P15

Saturday, October 4, 9:00 am — 10:30 am

P15 - Loudspeakers—Part 1

P15-1 Advanced Passive Loudspeaker Protection—Scott Dorsey, Kludge Audio - Williamsburg, VA, USAIn a follow-on to a previous conference paper (AES Convention Paper 5881), the author explores the use of polymeric positive temperature coefficient (PPTC) protection devices that have a discontinuous I/V curve that is the result of a physical state change. He gives a simple model for designing networks employing incandescent lamps and PPTC devices together to give linear operation at low levels while providing effective limiting at higher levels to prevent loudspeaker damage. Some discussion of applications in current service is provided.
Convention Paper 7588 (Purchase now)

P15-2 Target Modes in Moving Assemblies of Compression Drivers and Other Loudspeakers—Fernando Bolaños, Pablo Seoane, Acústica Beyma S.A. - Valencia, SpainThis paper deals with how the important modes in a moving assembly of compression drivers and other loudspeakers can be found. Dynamic importance is an essential tool for those who work on modal analysis of systems with many degrees of freedom and complex structures. The important modes calculation or measurement in moving assemblies is an objective (absolute) method to find the relevant modes that act on the dynamics of these transducers. Our paper discusses axial modes and breath modes, which are basic for loudspeakers. The model generalized masses and the participation factors are useful tools to find the moving assemblies important modes (target modes). The strain energy of the moving assembly, which represents the amount of available potential energy, is essential as well.
Convention Paper 7589 (Purchase now)

P15-3 Determining Manufacture Variation in Loudspeakers Through Measurement of Thiele/Small Parameters—Scott Laurin, Karl Reichard, Pennsylvania State University - State College, PA, USAThiele/Small parameters have become a standard for characterizing loudspeakers. Using fairly straightforward methods, the Thiele/Small parameters for twenty nominally identical loudspeakers were determined. The data were compiled to determine the manufacturing variations. Manufacturing tolerances can have a large impact on the variability and quality of loudspeakers produced. Generally, when more stringent tolerances are applied, there is less variation and drivers become more expensive. Now that the loudspeakers have been characterized, each one will be driven to failure. Some loudspeakers will be intentionally degraded to accelerate failures. The goal is to correlate variation in the Thiele/Small parameters with variation in speaker failure modes and operating life.
Convention Paper 7590 (Purchase now)

P15-4 About Phase Optimization in Multitone Excitations —Delphine Bard, Vincent Meyer, University of Lund - Lund, SwedenMultitone signals are often used as excitation for the characterization of audio systems. The frequency spectrum of the response consists of harmonics of the frequencies contained in the excitation and intermodulation products. Besides the choice of frequencies, in order to avoid frequency overlapping, there is also the need to chose adequate magnitudes and phases for the different components that constitute the multitone signal. In this paper we will investigate how the choice of the phases will impact the properties of the multitone signal, but also how it will affect the performances of a compensation method based on Volterra kernels and using multitone signals as an excitation.
Convention Paper 7591 (Purchase now)

P15-5 Viscous Friction and Temperature Stability of the Mid-High Frequency Loudspeaker—Ivan Djurek, Antonio Petosic, University of Zagreb - Zagreb, Croatia; Danijel Djurek, Alessandro Volta Applied Ceramics (AVAC) - Zagreb, CroatiaMid-high frequency loudspeakers behave quite differently as compared to low-frequency units, regarding effects coming from the surrounding air medium. Previous work stressed high influence of the imaginary part of the viscous force, which significantly affects the resonance frequency of mid-high frequency loudspeakers. Viscous force is relatively highly dependent on temperature and humidity of the surrounding air, and in this paper we have evaluated how changes in temperature and humidity reflect to the loudspeaker's linearity, which may be significant for the quality of sound reproduction.
Convention Paper 7592 (Purchase now)

P15-6 Calorimetric Evaluation of Intrinsic Friction in the Loudspeaker Membrane—Antonio Petosic, Ivan Djurek, University of Zagreb - Zagreb, Croatia; Danijel Djurek, Alessandro Volta Applied Ceramics (AVAC) - Zagreb, CroatiaFriction losses in the vibrating system of an electrodynamic loudspeaker are represented by the intrinsic friction Ri, which enters the equation of motion, and these losses are accompanied by irreversible release of the heat. A method is proposed for measurement of the friction losses in the loudspeaker's membrane by measurement of the thermocouple temperature probe glued to the membrane. Temperature on the membrane surface fluctuates stochastically as a result of thermo-elastic coupling in the membrane material. Evaluation of the amplitude in the temperature fluctuations enables an absolute and direct evaluation of intrinsic friction Ri entering friction force F=Ri·?(x), irrespective of the nonlinearity type and strength associated with the loudspeaker operation.
Convention Paper 7593 (Purchase now)

P15-7 Phantom Powering the Modern Condenser Microphone: A Practical Look at Conditions for Optimized Performance—Mark Zaim, Tadashi Kikutani, Jackie Green, Audio-Technica U.S., Inc.Phantom Powering a microphone is a decades old concept with powering conventions and methods that may have become obsolete, ineffective, or inefficient. Modern sound techniques, including those of live sound settings, now use many condenser microphones in settings that were previously dominated by dynamics. As a prerequisite for considering a modern phantom power specification or method, we study the efficiencies and requirements of microphones in typical multiple mic and high SPL settings in order to gain understanding of circuit and design requirements for the maximum dynamic range performance.
Convention Paper 7594 (Purchase now)